Century-Old TB Vaccine Ineffective Against COVID-19

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In the early days of the Covid-19 pandemic, when effective treatments and vaccines were still a distant hope, scientists began testing an old tuberculosis vaccine, known as B.C.G., against the coronavirus. The hope was that this vaccine, developed in the early 1900s to combat T.B. and was known to bolster the immune system, might be repurposed to protect against Covid-19. However, as new Covid vaccines were introduced, the trial enrolled fewer participants than expected, and the results were inconclusive.  

As per a recent study published in The New England Journal of Medicine, an old tuberculosis vaccine, known as B.C.G. for bacilli Calmette-Guerin, did not prevent COVID-19 infections among healthcare workers. Scientists began testing the vaccine early in the pandemic, hoping it might be repurposed to save lives. The B.C.G. vaccine was developed in the early 1900s to combat T.B., but it has since also been shown to confer protection against other illnesses, including respiratory diseases.  

As the pandemic progressed and there were no effective cures for COVID-19, a new vaccine against the highly contagious disease appeared to be a faraway fantasy when the trial of healthcare professionals began in March 2020. Six months following immunization with B.C.G., however, no significant differences were identified between the two groups of healthcare professionals, with 14.7% of those inoculated with B.C.G. acquiring symptomatic COVID-19 infections and 12.3% of those who received saline placebo shots becoming unwell.

One individual in the placebo group died, while five others required hospitalization. There was no statistically significant difference between the groups. The trial’s duration and sample size were shorter than expected, and the researchers noted that the findings did not rule out the possibility of additional vaccine advantages. The B.C.G. study could not be completed as anticipated because healthcare personnel was among the first to receive the newly accessible mRNA vaccinations.  

The original plan for the B.C.G. trial was to follow 10,000 patients from five countries annually. However, the most recent study only reported on 4,000 adults who were followed for six months. Dr. Nigel Curtis, the trial’s primary investigator and a professor of pediatric infectious diseases at the University of Melbourne in Australia, called the mRNA vaccines “an absolute miracle of modern science.” “From the perspective of the trial,” though, “it was pretty disastrous.” A more extensive study would have been required to evaluate whether the vaccine prevented not just COVID-19 infections but also hospitalizations and fatalities.  

The B.C.G. immunization protects many infants in developing countries with short life expectancies. According to the study, B.C.G. immunization reduces neonatal mortality. The vaccination protects infants from tuberculosis and teaches the immune system how to respond to other pathogens, lessening the occurrence of respiratory disorders and maybe other diseases. 

“The conclusion of our trial — that B.C.G. does not protect healthcare workers against mild or moderate COVID-19” is “true,” according to Dr. Curtis. Nonetheless, he stated, “This tells us nothing about the ability to protect people in other age groups against infections,” implying that the discovery is still promising. The notion of B.C.G. is still essential in neonatal development.  

The data gathered from the vaccinated healthcare workers is still being examined. Dr. Curtis cautioned that the vaccine’s efficiency could vary depending on the targeted bacteria. The B.C.G. immunization employs live, mutant bacteria generated during decades of experimental development in various sites worldwide. Different B.C.G. strains and inoculation techniques may explain divergent outcomes in other studies, according to some specialists.  

A small study of Type 1 diabetic patients found that many B.C.G. inoculations helped them control their blood sugar and protected them from infection before the pandemic. The researchers discovered that B.C.G. recipients had much lower incidences of COVID-19 infection than placebo recipients.  

The study’s principal researcher, Dr. Nigel Curtis, admitted that B.C.G. did not protect healthcare workers from mild or moderate Covid infections. He did, however, emphasize that immunization could be beneficial in preventing disease in persons of all ages. The B.C.G. vaccine, still widely used in developing countries, can reduce infant mortality and prevent other infections.



More research is being conducted into the data collected from inoculated healthcare workers, and the vaccine’s efficacy may be strain specific. While the trial’s results were disappointing regarding the B.C.G. vaccine’s ability to provide Covid-19 protection, they do not rule out its potential for other benefits.


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